1. Field of the invention
This invention relates to an apparatus for inspecting the outward appearance of an IC package stored in an embossed tape.
2. Description of the Related Art
The IC package made by a series of manufacturing steps are usually stored in an embossed tape employed as means for parts supply to e.g. an automounter, so that they may be picked up by the mounter head, and mounted on a wiring board. No proper mounting is, however, possible if any IC package stored in the embossed tape faces in the wrong direction, if any pin position is wrongly marked, if the embossed tape contains a different kind of IC package, or if any lead is bent, or undesirably floated or sunk. It is, therefore, necessary to inspect the outward appearance of any IC package stored in an embossed tape before its shipment.
FIG. 1 shows a known apparatus for inspecting the outward appearance of IC packages. The apparatus includes a mechanism not shown, but provided for moving an embossed tape 10, which is unwound from a reel not shown, intermittently by a predetermined distance in one direction as indicated by an arrow pointing to the left in FIG. 1, and an image forming camera 1 facing the embossed tape 10. The embossed tape 10 stores a plurality of IC packages P enclosed by a cover tape 2. As the embossed tape 10 is intermittently moved, the image of each package P is taken by the camera 1 through the cover tape 2, and used for the inspection of its outward appearance.
The known apparatus has, however, a number of drawbacks as pointed out below:
(1) If the cover tape 2 becomes loose, it causes the diffused reflection of light from a light source on its surface as shown by hatching in FIG. 2, and the hatched portions appear white in an image taken by the camera and disable the configuration of an IC package P to be clearly recognized;
(2) The position of any IC package P in the monitor area of the camera 1 is so unstable that, if, for example, vibration causes the package P to be inclined in the storage concavity 10a of the embossed tape 10 as shown in FIG. 2, a character string to be read from the position of a mark M as representing the type and kind of the package P disappears from the read area of the camera 1, resulting in the failure to identify the package P; and
(3) The sidewalls W of each storage concavity 10a of the embossed tape 10 are inclined for the convenience of its release from a device employed for making it, and if the inclination of any IC package P brings the free ends of its lead or leads L into contact with the sidewalls W, the virtual images of the leads L are formed on the sidewalls W as shown in FIG. 3, and make it impossible to inspect the leads L properly to see if they are bent, or raised or depressed. When a lead appears long, it normally means that the lead is floating. In this situation, conventional recognition systems judge it to be a defective lead, even though it is a good lead.